[PATCH 0/3] serial: 8250: Add Loongson-2K0300 and Loongson-2K3000 UART support

[PATCH 0/3] serial: 8250: Add Loongson-2K0300 and Loongson-2K3000 UART support

[Binbin Zhou]

Hi all:

This series adds UART support for two Loongson SoCs.

The Loongson-2K0300 UART is the same as the one found on the
Loongson-2K1500, so it is documented as falling back to
"loongson,ls2k1500-uart" and then "ns16550a". No driver changes are
needed.

The Loongson-2K3000 UART differs from earlier Loongson UARTs in that it
does not require MCR/MSR signal inversion. It also supports a fractional
baud rate divisor. A dedicated compatible and driver data are added so
the driver can distinguish it.

Thanks.
Binbin

Binbin Zhou (3):
  dt-bindings: serial: 8250: Document Loongson-2K0300 UART compatible
  dt-bindings: serial: 8250: Add dedicated Loongson-2K3000 UART
    compatible
  serial: 8250_loongson: Add Loongson-2K3000 UART support

 Documentation/devicetree/bindings/serial/8250.yaml | 4 ++++
 drivers/tty/serial/8250/8250_loongson.c            | 7 +++++++
 2 files changed, 11 insertions(+)


base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.52.0

[PATCH 1/3] dt-bindings: serial: 8250: Document Loongson-2K0300 UART compatible

[Binbin Zhou]

The UART on the Loongson-2K0300 SoC is identical to the Loongson-2K1500
UART. Document the SoC-specific compatible `loongson,ls2k0300-uart`
with fallback to `loongson,ls2k1500-uart` and then `ns16550a`.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
---
 Documentation/devicetree/bindings/serial/8250.yaml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
index 50d5c977afa3..01abd39509a7 100644
--- a/Documentation/devicetree/bindings/serial/8250.yaml
+++ b/Documentation/devicetree/bindings/serial/8250.yaml
@@ -192,6 +192,7 @@ properties:
               - loongson,ls3a4000-uart
               - loongson,ls3a5000-uart
               - loongson,ls3a6000-uart
+              - loongson,ls2k0300-uart
               - loongson,ls2k2000-uart
           - const: loongson,ls2k1500-uart
           - const: ns16550a
-- 
2.52.0

[PATCH 2/3] dt-bindings: serial: 8250: Add dedicated Loongson-2K3000 UART compatible

[Binbin Zhou]

Unlike earlier Loongson UARTs, the Loongson-2K3000 UART does not require
MCR/MSR signal inversion. Add a dedicated compatible so the driver can
distinguish it from the existing Loongson UART variants.

Document `loongson,ls2k3000-uart` with `ns16550a` as fallback.

Signed-off-by: Haowei Zheng <zhenghaowei@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
---
 Documentation/devicetree/bindings/serial/8250.yaml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
index 01abd39509a7..33c13c48ed56 100644
--- a/Documentation/devicetree/bindings/serial/8250.yaml
+++ b/Documentation/devicetree/bindings/serial/8250.yaml
@@ -196,6 +196,9 @@ properties:
               - loongson,ls2k2000-uart
           - const: loongson,ls2k1500-uart
           - const: ns16550a
+      - items:
+          - const: loongson,ls2k3000-uart
+          - const: ns16550a
       - items:
           - enum:
               - aspeed,ast2600-vuart
-- 
2.52.0

Re: [PATCH 2/3] dt-bindings: serial: 8250: Add dedicated Loongson-2K3000 UART compatible

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] dt-bindings: serial: 8250: duplicate ns16550a fallback block for ls2k3000
--

commit 71974153fe22bc00d365059be9198364c9cfaa86
Author: Binbin Zhou <zhoubinbin@loongson.cn>

dt-bindings: serial: 8250: Add dedicated Loongson-2K3000 UART compatible

This commit documents the loongson,ls2k3000-uart compatible string with
ns16550a as a fallback so the driver can distinguish the Loongson-2K3000 UART
from earlier Loongson UARTs that require MCR/MSR signal inversion.

> diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
> index 01abd39509a7a..33c13c48ed56e 100644
> --- a/Documentation/devicetree/bindings/serial/8250.yaml
> +++ b/Documentation/devicetree/bindings/serial/8250.yaml
> @@ -196,6 +196,9 @@ properties:
>                - loongson,ls2k2000-uart
>            - const: loongson,ls2k1500-uart
>            - const: ns16550a
> +      - items:
> +          - const: loongson,ls2k3000-uart
> +          - const: ns16550a

[Severity: Low]
This isn't a bug, but properties:compatible in
Documentation/devicetree/bindings/serial/8250.yaml already has a two-item
block with const: ns16550a as the fallback that includes the other base
Loongson UART compatibles:

      - items:
          - enum:
              ...
              - loongson,ls2k0500-uart
              - loongson,ls2k1500-uart
          - const: ns16550a

Could loongson,ls2k3000-uart be added to that existing enum instead of adding
a separate two-item block?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1793776192.git.zhoubinbin@loongson.cn?part=2

[PATCH 3/3] serial: 8250_loongson: Add Loongson-2K3000 UART support

[Binbin Zhou]

The Loongson-2K3000 UART differs from earlier Loongson UARTs in that it
does not require MCR/MSR signal inversion. It also supports a fractional
baud rate divisor.

Add the corresponding OF match entry for `loongson,ls2k3000-uart` so the
driver can probe with the new driver data.

Signed-off-by: Haowei Zheng <zhenghaowei@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
---
 drivers/tty/serial/8250/8250_loongson.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_loongson.c b/drivers/tty/serial/8250/8250_loongson.c
index 6d06ed28382d..0458a9f82d86 100644
--- a/drivers/tty/serial/8250/8250_loongson.c
+++ b/drivers/tty/serial/8250/8250_loongson.c
@@ -43,6 +43,12 @@ static const struct loongson_uart_ddata ls2k1500_uart_data = {
 	.msr_invert = 0,
 };
 
+static const struct loongson_uart_ddata ls2k3000_uart_data = {
+	.has_frac = true,
+	.mcr_invert = 0,
+	.msr_invert = 0,
+};
+
 struct loongson_uart_priv {
 	struct uart_8250_port *uport;
 	struct clk *clk;
@@ -216,6 +222,7 @@ static DEFINE_SIMPLE_DEV_PM_OPS(loongson_uart_pm_ops, loongson_uart_suspend,
 static const struct of_device_id loongson_uart_of_ids[] = {
 	{ .compatible = "loongson,ls2k0500-uart", .data = &ls2k0500_uart_data },
 	{ .compatible = "loongson,ls2k1500-uart", .data = &ls2k1500_uart_data },
+	{ .compatible = "loongson,ls2k3000-uart", .data = &ls2k3000_uart_data },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, loongson_uart_of_ids);
-- 
2.52.0

Re: [PATCH 0/3] serial: 8250: Add Loongson-2K0300 and Loongson-2K3000 UART support

[Huacai Chen]

For this series:

Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>

On Wed, Nov 4, 2026 at 3:46 PM Binbin Zhou <zhoubinbin@loongson.cn> wrote:
>
> Hi all:
>
> This series adds UART support for two Loongson SoCs.
>
> The Loongson-2K0300 UART is the same as the one found on the
> Loongson-2K1500, so it is documented as falling back to
> "loongson,ls2k1500-uart" and then "ns16550a". No driver changes are
> needed.
>
> The Loongson-2K3000 UART differs from earlier Loongson UARTs in that it
> does not require MCR/MSR signal inversion. It also supports a fractional
> baud rate divisor. A dedicated compatible and driver data are added so
> the driver can distinguish it.
>
> Thanks.
> Binbin
>
> Binbin Zhou (3):
>   dt-bindings: serial: 8250: Document Loongson-2K0300 UART compatible
>   dt-bindings: serial: 8250: Add dedicated Loongson-2K3000 UART
>     compatible
>   serial: 8250_loongson: Add Loongson-2K3000 UART support
>
>  Documentation/devicetree/bindings/serial/8250.yaml | 4 ++++
>  drivers/tty/serial/8250/8250_loongson.c            | 7 +++++++
>  2 files changed, 11 insertions(+)
>
>
> base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
> --
> 2.52.0
>